10 Among the Ancient Glaciers of North Wales. 
in the most critical manner upon slopes which seem too steep to 
give them support— still more clearly and unmistakably exhibited. 
The transported blocks and glacier scratches in the Vale of Llan- 
berris are so well known to geologists that I simply refer to them to 
call to the mind of the reader the general aspect of the phenomena 
which I am about to describe as occurring in other parts of the 
Snowdon district, where they are not so well known, or so univer- 
sally ascribed to the action of an extinct system of glaciers. Just at 
the top of the Vale of Llanberris, there is a hollow in the profile of 
the ridge which forms its northern boundary. It lies exactly be- 
tween the cluster of houses called Gorphwysfa on the south, and 
the lake of Cym-ffynnen, at the base of the two Glyders, on the 
north. A few hundred yards to the east or southeast of the lowest 
part, at a distance of not more than 300 yards from the great block 
of the Vale of Llanberris, there is a little round knoll of rock which 
rises by itself above the neighboring parts of the ridge. It is some- 
thing like an inverted basin, so that the ground falls away pretty 
steeply on either side, and the top is nowhere less than fifteen or 
twenty feet higher than the surrounding parts. Perched on the 
very top of this knoll, resting on three points of contact at most, is 
an irregular piece of rock, of a different formation from that upon 
wliich it rests, seven or eight feet long, three or four broad, and as 
many high. It has never been subjected to any process of abrasion 
or rounding, for every corner is perfectly sharp and angular— pre- 
senting in this respect a marked contrast to the rock on which it 
rests, which is round and smooth, and somewhat weather-worn. 
What could have brought this block to its resting-place? To have 
rolled thither it must have rolled some twenty-five feet up-hill, 
from whatever direction it had come. The ridge, for some hundreds 
of yards on either side of the knoll, rises but gently, and presents 
an undulating surface, along which a sharp oblong, irregular block 
of stone could by no possibility have preserved for any distance a 
considerable velocity: and between this knoll and the spur of the 
Glyder Fawr — the only considerable altitude within a mile of the 
spot — there is a hollow at least 150 feet in depth. But a little l)elow 
the top of the knoll, on its eastern slope, is a still more remarkable 
block. It is about the same size as that which is seated on the 
summit of the knoll, and similarly sharp and angular, but consists 
of a coarse conglomerate of a very marked and peculiar kind, in 
which large round white pebbles, apparently of quartz, are imbedded 
in a kind of matrix, which looks like a coarse red sandstone. The 
